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End Show 17-1 The Fossil Record Slide 2 of 40 Fossils and Ancient Life What is the fossil record?

End Show Slide 3 of The Fossil Record Copyright Pearson Prentice Hall Fossils and Ancient Life The fossil record provides evidence about the history of life on Earth. It also shows how different groups of organisms, including species, have changed over time.

End Show Slide 4 of The Fossil Record Copyright Pearson Prentice Hall Fossils and Ancient Life The fossil record provides incomplete information about the history of life. Over 99% of all species that have lived on Earth have become extinct, which means that the species has died out. Those species that still exist are referred to as being extant.

End Show Slide 5 of The Fossil Record Copyright Pearson Prentice Hall How Fossils Form Most fossils form in sedimentary rock. Sedimentary rock forms when exposure to the elements breaks down existing rock into small particles of sand, silt, and clay.

End Show Slide 6 of The Fossil Record Copyright Pearson Prentice Hall How Fossils Form Fossil Formation Water carries small rock particles to lakes and seas.

End Show Slide 7 of The Fossil Record Copyright Pearson Prentice Hall How Fossils Form Dead organisms are buried by layers of sediment, which forms new rock.

End Show Slide 8 of The Fossil Record Copyright Pearson Prentice Hall How Fossils Form The preserved remains may be later discovered and studied.

End Show Slide 9 of The Fossil RecordInterpreting Fossil Evidence Paleontologists determine the age of fossils using relative dating or radioactive dating.

End Show Slide 10 of The Fossil Record Copyright Pearson Prentice Hall Interpreting Fossil Evidence Relative Dating In relative dating, the age of a fossil is determined by comparing its placement with that of fossils in other layers of rock. Rock layers form in order by age—the oldest on the bottom, with more recent layers on top.

End Show Slide 11 of The Fossil Record Copyright Pearson Prentice Hall Interpreting Fossil Evidence Relative Dating

End Show Slide 12 of The Fossil RecordInterpreting Fossil Evidence Index fossils are used to compare the relative ages of fossils. An index fossil is a species that is recognizable and that existed for a short period but had a wide geographic range.

End Show Slide 13 of The Fossil Record Copyright Pearson Prentice Hall Interpreting Fossil Evidence Radioactive Dating Scientists use radioactive decay to assign an absolute age to rocks. Radioactive dating is the use of half-lives to determine the age of a sample. A half-life is the length of time required for half of the radioactive atoms in a sample to decay.

End Show Slide 14 of The Fossil Record Copyright Pearson Prentice Hall Interpreting Fossil Evidence

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End Show Slide 16 of The Fossil Record Copyright Pearson Prentice Hall Geologic Time Scale The basic divisions of the geologic time scale are eras and periods.

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End Show Slide 18 of The Fossil RecordGeologic Time Scale Geologic time begins with Precambrian Time, which covers about 88% of Earth’s history. Vendian 650–544

End Show Slide 19 of The Fossil Record Copyright Pearson Prentice Hall Geologic Time Scale Eras Geologists divide the time between Precambrian time and the present into three eras: Paleozoic Era Mesozoic Era Cenozoic Era

End Show Slide 20 of The Fossil Record Copyright Pearson Prentice Hall Geologic Time Scale Permian Carboniferous Devonian Silurian Ordovician Cambrian 290– – – – – –505

End Show Slide 21 of The Fossil RecordGeologic Time Scale Cretaceous Jurassic Triassic 145–65 208– –208

End Show Slide 22 of The Fossil RecordGeologic Time Scale

End Show Slide 23 of The Fossil Record Copyright Pearson Prentice Hall Geologic Time Scale

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End Show 17-1 The Fossil Record Slide 30 of 40 Copyright Pearson Prentice Hall Geologic Time Scale Clock Model of Earth’s History First humans First prokaryotes Cenozoic Era Mesozoic Era Paleozoic Era Precambrian Time First land plants First multicellular organisms First eukaryotes Radiation of mammals Accumulation of atmospheric oxygen

End Show - or - Continue to: Click to Launch: Slide 31 of 40 Copyright Pearson Prentice Hall 17-1

End Show Slide 32 of 40 Copyright Pearson Prentice Hall 17-1 Which of the following statements about fossils is NOT true? a.Most fossils form in sedimentary rock. b.Fossils occur in a particular order. c.Only a small portion of fossils are from extinct organisms. d.Fossils can be used in relative dating of rock formations.

End Show Slide 33 of 40 Copyright Pearson Prentice Hall 17-1 The fossil record consistently shows evidence that a.all forms of life have existed in all geologic eras. b.living organisms have only been on Earth for a short time. c.living things have changed over time. d.ancient life-forms are much the same as forms found living today.

End Show Slide 34 of 40 Copyright Pearson Prentice Hall 17-1 Index fossils assist paleontologists in dating rocks because they represent species that a.were widely distributed and existed for a very long time. b.existed in a single location for a short period of time. c.were widely distributed and existed for a short time. d.existed in a single location for a very long time.

End Show Slide 35 of 40 Copyright Pearson Prentice Hall 17-1 Determining the age of a fossil by comparing its placement with fossils in other layers of rock is called a.carbon-14 dating. b.fossil-indexing. c.relative dating. d.absolute dating.

End Show Slide 36 of 40 Copyright Pearson Prentice Hall 17-1 According to the geologic time scale, geologic time begins with a.Precambrian Time. b.the Paleozoic Era. c.the Quaternary Period. d.the Cambrian Era.

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